For Medium-Size Rooms: Frigidaire FFRE0833S1

This 8,000-BTU window air conditioner cools rooms up to 350 square feet and received 4 stars from Lowe's shoppers, who cited its high quality, durability, ease of installation, and quiet operation. The unit boasts three fan speeds, remote control, a special sleep mode, 24-hour on/off timer, and a clean-filter alert. Available on Amazon; $299.